This invention relates to a process for silicon etch damage reduction.
It is known in the prior art that the manufacture of semiconductor devices typically involves patterned etching using liquid or wet etching materials, such halogens or halogen-containing compounds, of certain layers which comprise features of these devices. For example, one well known etching material is chlorine which can exist in the etching process as either chlorine gas or HCl, etc. Chlorine etches the semiconductor isotropically, i.e., in both a lateral and vertical direction. This results in an etched feature which has a line width which is smaller than the resist image.
Etching can also be conducted in a gas phase using known techniques such as plasma etching, ion beam etching, and reactive ion etching. The use of gas plasma technology provides substantially anisotropic etching using gaseous ions, typically generated by an RF discharge. In gas plasma etching the requisite portion of the surface to be etched is removed by a chemical reaction between the gaseous ions and the subject surface. In the anisotropic process, etching takes place only or primarily in the vertical direction so that feature widths substantially match the photoresist pattern widths.
Semiconductor structures can include a layer of silicon dioxide grown and/or deposited on an underlying silicon substrate. However, plasma etching of silicon dioxide on silicon is known to cause silicon lattice damage due to bombardment effects of ions, energetic neutrals, radicals, and other plasma species. The effect of silicon damage has been determined to degrade gate oxide integrity and interfere with oxidation growth rates. Current techniques to reduce damage are focused on the etcher design and etch process parameters and are successful only to varying degrees.
Therefore, a need exists for a process which significantly reduces silicon etch damage that is detrimental to semiconductor device performance. Silicon damage after plasma etching has been linked to multiple integrated circuit fabrication problems such as incomplete oxide regrowth, silicide formation problems, contact resistance problems and many more.